Conventionally, a work state monitoring device has been used for an operator to monitor the work state of a work vehicle such as a crane.
Some of the conventional work state monitoring devices which are configured to generate a graph of total rated weights (at 100% load factor) related to working radiuses are taught by, for example, Japanese Patent No. 3,136,110. In the work state monitoring device of this conventional technique, when the current weight is close to or even surpasses the total rated weight, the work is forcibly terminated and the weight is decreased to be within a range indicated by the graph.
In other work state monitoring devices, operators are warned by, for example a yellow light installed on the work vehicle when the current weight is close to the total rated weight, and the operators are warned by a red light when the current weight reaches the total rated weight.